JP2014137542A - Fixing device and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive fixing device capable of suppressing both a change in conveyance speed of a recording medium and a reduction in durability of a fixing belt, and an image forming apparatus including the fixing device.SOLUTION: A fixing device 100 includes an endless fixing belt 14, a fixing roller 11, and a heating roller 12. The fixing belt 14 is laid over the fixing roller 11 and the heating roller 12. The fixing device 100 additionally includes a rotatable pressure roller 15 that is arranged to press an outer peripheral surface thereof against an outer peripheral surface of the fixing roller 11 with the fixing belt 14 therebetween, and a driving unit 30 that drives to rotate the fixing roller 11 to rotationally move the fixing belt 14. The fixing device 100 further includes a rotation number detection unit 40 that detects the number of rotation of the heating roller 12, and a control unit 50 that controls the rotational drive of the fixing roller 11 by the driving unit 30 on the basis of the number of rotation of the heating roller 12 detected by the rotation number detection unit 40.

Description

  The present invention relates to a fixing device and an image forming apparatus including the fixing device.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a composite machine thereof, an electrostatic latent image formed on an image carrier is developed by a developing device, and the toner image is transferred onto a recording medium. In some cases, the image is formed by fixing with a fixing device.

  Various fixing devices have been proposed. For example, a fixing device employing a belt fixing method is known. The fixing device of the belt fixing system includes a fixing roller, a heating roller, an endless fixing belt stretched between the fixing roller and the heating roller, and the fixing roller so that the fixing belt is sandwiched between the fixing roller. And a pressure roller disposed opposite to the main body. The fixing device heats and presses a sheet as a recording medium on which an unfixed toner image is formed as it passes through a nip portion formed by pressure contact between a pressure roller and a fixing belt, thereby unfixing the sheet. Fix the toner image on the sheet. Such a belt-fixing type fixing device is disclosed in, for example, Patent Document 1.

  Here, sheet conveyance in fixing will be described with reference to FIG.

  FIG. 5 is a diagram showing a schematic configuration of a conventional fixing device. This fixing device (indicated by reference numeral 800 in the figure) includes a fixing roller 811, a heating roller 812, and an endless fixing belt 814 stretched between the fixing roller 811 and the heating roller 812. . In addition, the fixing device 800 includes a pressure roller 815 disposed opposite to the fixing roller 811 so that the fixing belt 814 is sandwiched between the fixing roller 811, a motor 801 and a gear 802 that apply a rotational force to the fixing roller 811. It is equipped with.

  In the fixing device 800, a rotational force is applied to the fixing roller 811 by a motor 801 and a gear 802, and when a sheet P as a recording medium enters the pressure contact portion N of the pressure roller 815 facing the fixing roller 811, The sheet P is conveyed by the clamping force of the press contact portion N.

  Here, the speed at which the sheet P is sent out at the press-contact portion N is the speed at which the sheet P is sent out when the diameter of the fixing roller 811 or the pressure roller 815 is increased due to thermal expansion or the like even if the rotational speed of the motor is constant. Will be faster. When the speed of the sheet fed from the fixing device 800, that is, the conveyance speed of the fixing device 800 fluctuates, the relative linear velocity of the sheet with various devices arranged upstream or downstream of the fixing device 800 ( A shift in the movement speed) occurs.

  When such a relative linear velocity shift occurs, for example, when the conveyance speed of the fixing device 800 increases, the sheet loosens with the downstream device (for example, a paper discharge device). Image damage may occur due to strong contact with the conveyance guide. Further, when the speed of the fixing device 800 is slow, the sheet may be stretched between the downstream devices and wrinkles may occur.

  In recent years, due to increased awareness of environmental issues, the use of thin paper, which uses less pulp as a sheet and generates less carbon dioxide during papermaking, and the expansion of markets such as production printing, the ability to respond from thin paper to thick paper, High speed has been demanded. However, since the quality of production printing is required to be as high as that of offset printing, the above-described deterioration in quality has become unacceptable.

  For this reason, for example, in the fixing device disclosed in Patent Document 1, in order to keep the speed of the sheet conveyed by the fixing device constant, the temperature of the core metal of the fixing roller is detected to predict the radial expansion of the fixing roller. Some measures have been taken, such as determining the motor speed. Specifically, a thermistor is brought into contact with the cored bar of the fixing roller, and a correlation between the cored bar temperature and the sheet linear velocity is measured in a preliminary experiment and used as a correction value. It was. However, in the method of determining the rotation speed of the fixing roller by detecting the temperature of the core metal of the fixing roller, the temperature of the core metal also depends on the ambient temperature, and the thermal expansion amount of the fixing roller can be accurately predicted. was difficult. Therefore, there is a problem that it is difficult to suppress fluctuations in the sheet conveyance speed. In the fixing device, even if the pressure contact force is constant, the sheet P tends to be faster when it is thicker than thin paper, and faster than the non-coated sheet. It was not able to cope with fluctuations in the conveyance speed due to differences in the thickness of the sheet P and the like.

  Therefore, in the fixing device disclosed in Patent Document 2, a pressure sensor is disposed in the pressure contact portion, and the pressure roller output is increased by utilizing the fact that the pressure sensor diameter increases as the pressure roller diameter expands due to thermal expansion. The number of rotations is controlled to be constant. However, even in the fixing device of Patent Document 2, there is a large variation in detection accuracy by the pressure sensor due to the influence of wear due to sliding of the pressure plate and the like, and it is difficult to accurately control the rotation speed of the pressure roller. Therefore, there is a problem that it is difficult to suppress fluctuations in the sheet conveyance speed.

  Patent Documents 3 and 4 disclose techniques applicable to solving such problems.

  In the fixing device disclosed in Patent Document 3, a plurality of holes are formed at equal intervals in one end portion of an endless film as a fixing belt, and masking for shielding light from the entire periphery of the end portion is performed. Processing has been applied. In this fixing device, the peripheral speed of the endless film is detected by a photo interrupter. The fixing device disclosed in Patent Document 4 includes a rotation transmission device having a roller that rotates following the rotation of the fixing belt, and detects the rotation state of the fixing belt based on the output of the rotation transmission device. .

  By applying the techniques of the cited documents 3 and 4, it is conceivable to detect the linear speed (surface movement speed) of the fixing belt and control the rotation speed of the fixing roller or the like so as to make it constant.

  However, in the fixing device disclosed in the cited document 3, since a plurality of holes are formed in the endless film, the tensile strength is greatly reduced and the durability is lowered. Further, since the endless film needs to be masked for light shielding, the manufacturing cost is increased. In the fixing device disclosed in the cited document 4, since the fixing belt is sandwiched between the roller and the path forming surface, the fixing belt is worn and the durability is lowered. These problems are listed as examples.

  SUMMARY An advantage of some aspects of the invention is to provide an inexpensive fixing device that can suppress both a change in the conveyance speed of a recording medium and a decrease in durability of the fixing belt, and an image forming apparatus including the fixing device.

  In order to solve the above-mentioned problem, the invention described in claim 1 is characterized in that an endless fixing belt and the fixing belt are stretched and rotated as the fixing roller and the fixing belt rotate. A roller group including a plurality of driven rollers, a rotatable pressure member arranged to press the outer peripheral surface of the fixing roller against the outer peripheral surface of the fixing roller via the fixing belt, and the fixing belt are rotated. As described above, the driving means for rotationally driving at least one of the fixing roller and the pressing member, and the rotational speed detecting means for detecting the rotational speed of at least one driven roller of the one or more driven rollers. And control means for controlling the rotational drive by the drive means based on the rotational speed of the driven roller detected by the rotational speed detection means. A fixing device for.

  According to the first aspect of the present invention, at least one of the fixing roller and the pressure member is rotationally driven by the driving unit so that the fixing belt is rotated. The rotation speed detecting means detects the rotation speed of at least one driven roller included in the roller group on which the fixing belt is stretched. Then, based on the detected number of rotations of the driven roller, the control means controls the rotational drive of at least one of the fixing roller and the pressure member by the drive means. With such a configuration, the rotational speed of the driven roller on which the fixing belt is stretched has a correlation with the linear speed (surface movement speed) of the fixing belt, so that the linear speed of the fixing belt is grasped based on the rotational speed. be able to. Therefore, by controlling the driving means based on the number of rotations of the driven roller, the linear velocity of the fixing belt can be grasped without processing the fixing belt or adding a member such as a roller. Fluctuations can be suppressed. Accordingly, it is possible to suppress both a change in the conveyance speed of the recording medium and a decrease in durability of the fixing belt with an inexpensive configuration.

1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. 3 is a graph showing an example of the relationship between the thickness of a sheet passed through the fixing device of FIG. 2 is a graph showing an example of the relationship between the number of rotations of a heating roller of the fixing device of FIG. 1 is a schematic configuration diagram of a tandem type color copier that is an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of the conventional fixing device.

(Embodiment of fixing device)
Hereinafter, a fixing device according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic configuration diagram of a fixing device according to an embodiment of the present invention. FIG. 2 is a graph showing an example of the relationship between the thickness of the sheet passed through the fixing device of FIG. 1 and the number of rotations of the heating roller. FIG. 3 is a graph showing an example of the relationship between the number of rotations of the heating roller of the fixing device of FIG. 1 and the linear velocity of the sheet passing through the fixing device.

  As shown in FIG. 1, the fixing device 100 includes a fixing roller 11, a heating roller 12, a tension roller 13, a fixing belt 14, a pressure roller 15, a photo sensor 16, a cleaning mechanism 17, and a first mechanism. A separation claw 18 and a second separation claw 19 are provided. The fixing device 100 also includes a drive unit 30 that rotationally drives the fixing roller 11, a rotation number detection unit 40 that detects the rotation number of the heating roller 12, and a control unit 50 that controls the drive unit 30. .

  The fixing roller 11 is provided with an elastic layer 11b such as silicone rubber on a metal core 11a made of aluminum (including aluminum alloy) or iron. For the elastic layer 11b of the fixing roller 11, foamed silicone rubber may be used so that the heat of the fixing belt 14 is not easily absorbed in order to shorten the warm-up time.

  The heating roller 12 is a hollow roller made of aluminum or iron, and is opposed to the fixing roller 11 with an interval so that the shafts are parallel to each other. The heating roller 12 has a heat source including a heater 12h such as a halogen heater inside. The heat source may be an induction heating mechanism (IH). The heating roller 12 has a negligible thermal expansion compared to the fixing roller 11 having an elastic layer. Alternatively, the heater serving as the heat source may be disposed not on the heating roller 12 but on the outer peripheral surface of the fixing belt 14. As long as the object of the present invention is not violated, the configuration and arrangement of the heat source for heating the fixing belt 14 are arbitrary. The heating roller 12 corresponds to an example of a driven roller.

  The tension roller 13 is a hollow roller made of metal such as aluminum or iron or resin. The tension roller 13 has shafts parallel to each other between the fixing roller 11 and the heating roller 12 so that the shaft does not fall within a single plane including the shafts of the fixing roller 11 and the heating roller 12. They are offset. The tension roller 13 corresponds to an example of a driven roller. The fixing roller 11, the heating roller 12, and the tension roller 13 correspond to an example of a roller group.

  The fixing belt 14 is an endless belt, and has a two-layer structure in which an elastic layer such as a silicone rubber layer is formed on a base material such as nickel, stainless steel, or polyimide. The fixing belt 14 is stretched around the fixing roller 11, the heating roller 12 and the tension roller 13 with a certain tension. Further, the inner peripheral surface of the fixing belt 14 and the outer peripheral surface of the heating roller 12 (that is, the driven roller whose rotation speed is detected) are set in a frictional relationship in which no slip occurs. Since the heating roller 12 is rotated by the rotational movement of the fixing belt 14, the linear speed (surface moving speed) of the fixing belt 14 has a correlation with the rotational speed (rotational speed) of the heating roller 12. The fixing belt 14 corresponds to an example of a fixing member.

  The pressure roller 15 is a cylindrical roller in which an elastic layer 15b such as silicone rubber is provided on a metal core 15a made of aluminum or iron. The pressure roller 15 is rotatably arranged on the lower side in the figure with respect to the fixing belt 14, and its outer peripheral surface is pressed against the outer peripheral surface of the fixing roller 11 via the fixing belt 14. The pressure roller 15 forms a fixing pressure contact portion N between the pressure roller 15 and the fixing belt 14. The pressure roller 15 corresponds to an example of a pressure member.

  Further, the pressure roller 15 can be moved to the fixing belt 14 side by a pressure depressurizing means (not shown) to apply pressure, and can be moved in a direction away from the fixing belt 14 to be depressurized. During the fixing operation, the pressure roller 15 is pressed toward the fixing belt 14 by the pressure depressurizing means and pressed against the fixing belt 14 with a constant pressure. In the present embodiment, the form of the pressure roller 15 (roller type) is shown as the pressure member. However, the present invention is not limited to this, and the endless belt-like pressure member (belt) stretched over a plurality of rollers is not limited thereto. Type). As long as the pressurizing member is not contrary to the object of the present invention, as long as it is a rotatable member arranged to press the outer peripheral surface of the fixing roller 11 against the outer peripheral surface of the fixing roller 11 via the fixing belt 14, the configuration thereof is arbitrary. It is.

  The photo sensor 16 is disposed downstream of the fixing pressure contact portion N in the conveyance direction. The photosensor 16 detects the leading edge and the trailing edge of the sheet P as an example of a recording medium, and outputs a detection signal corresponding to the detection to the control unit 50 described later. The control unit 50 can detect the passage of the front and rear ends of the sheet P based on the detection signal from the photosensor 16 and can measure the speed of the sheet P based on the passage time of the front and rear ends. .

  The cleaning mechanism 17 cleans the pressure roller 15 by pressing a cleaning web. The first separation claw 18 is disposed on the sheet discharge side of the fixing pressure contact portion N and the tip thereof is in contact with the pressure roller 15 to prevent the sheet P from being wound around the pressure roller 15. The second separation claw 19 is disposed on the sheet P discharge side of the fixing pressure contact portion N and the tip thereof is disposed close to the fixing belt 14 to prevent the sheet P from being wound around the fixing belt 14.

  The drive unit 30 includes a motor 31 and a gear 32, and rotationally drives the fixing roller 11 based on a control signal from a control unit 50 described later. When the fixing roller 11 is driven to rotate, the fixing belt 14 rotates. Alternatively, the drive unit 30 may be configured to rotationally drive the pressure roller 15 instead of the fixing roller 11, or may be configured to rotationally drive both the fixing roller 11 and the pressure roller 15. It may be. The drive unit 30 corresponds to an example of a drive unit.

  The rotation speed detection unit 40 includes a filler 41 and a heating roller rotation detection sensor 42. The filler 41 is provided on the rotation shaft portion 12a of the heating roller 12, and is rotated integrally with the rotation shaft portion 12a. The heating roller rotation detection sensor 42 is composed of a photo interrupter, and is arranged so that the filler 41 passes between the light emitting unit and the light receiving unit as the heating roller 12 rotates. Thereby, the rotation speed detection unit 40 changes the detection signal output from the heating roller rotation detection sensor 42 every time the heating roller 12 rotates once. The rotation speed detection unit 40 corresponds to an example of a rotation speed detection unit.

  The control unit 50 is composed of, for example, a microcomputer. For example, the control unit 50 receives the detection signal from the rotation number detection unit 40 and calculates the rotation number of the heating roller 12 based on the detection signal. Further, the control unit 50 outputs a control signal to the drive unit 30 so as to rotate the fixing belt 14 at a target speed. Further, the control unit 50 may output a rotation number signal indicating the rotation number of the heating roller 12 to a display unit of the image forming apparatus described later. As a result, the rotation number of the heating roller 12 is displayed on the display unit of the image forming apparatus and shown to the maintenance worker or the like. The linear velocity of the fixing belt 14 can be adjusted by grasping the speed. The control unit 50 corresponds to an example of a control unit.

  Next, an example of a fixing operation in the fixing device 100 will be described.

  In the fixing device 100, during the fixing operation, the drive unit 30 drives the fixing roller 11 to rotate in the clockwise direction in the drawing based on a control signal from the control unit 50. Then, the fixing belt 14 is rotated and moved in the direction of discharging the sheet P (clockwise direction in the drawing) in a state where an appropriate tension is applied, and the pressure roller 15, the heating roller 12, and the tension roller 13 are rotated. . Further, the fixing belt 14 is heated to a predetermined temperature (for example, a temperature suitable for toner fixing) by the heat generated by the heater 12 h disposed inside the heating roller 12.

  In this manner, in the fixing device 100, the fixing belt 14 is rotated, the pressure roller 15 and the heating roller 12 are rotated, and the surface of the fixing belt 14 is heated to a predetermined temperature. In this state, when a sheet P on which an unfixed toner image is formed is passed through the fixing pressure contact portion N (paper passing from the right side to the left side in the drawing), the fixing pressure contact portion N is not fixed due to pressurization and heating. The toner image is thermally fused on the sheet P and fixed on the sheet P.

  The sheet P on which the toner image is fixed is discharged from the fixing pressure contact portion N. At this time, the sheet P may come out while being wound around the fixing belt 14 or the pressure roller 15. For this reason, the leading ends of the first separation claw 18 and the second separation claw 19 come into contact with the leading end portion of the sheet P, so that the sheet P is separated from the fixing belt 14 or the pressure roller 15. The sheet P discharged from the fixing pressure contact portion N is sent out from the fixing device 100 through a predetermined discharge path.

  Next, an example of the operation of the control unit 50 in the fixing device 100 will be described.

  When the fixing roller 11 is rotated, the fixing belt 14 is rotated by the frictional force with the fixing roller 11, and the heating roller 12 is further rotated by the frictional force with the fixing belt 14. Here, the outer peripheral surface of the heating roller 12 and the inner peripheral surface of the fixing belt 14 are set to have a frictional relationship that does not cause slipping. Therefore, the rotational speed of the heating roller 12 and the linear velocity of the fixing belt 14 are correlated (proportional relationship). )have. Therefore, when the fixing belt 14 and the heating roller 12 are in a proportional relationship, the linear speed of the fixing belt 14, that is, the linear speed (conveying speed) of the sheet P can be converted by measuring the rotation speed of the heating roller 12. Can do.

  Prior to the fixing operation, the control unit 50 performs preliminary measurement for controlling the drive unit 30. Specifically, the control unit 50 controls the pressurizing / depressurizing unit to press the pressure roller 15 against the fixing roller 11 via the fixing belt 14, and controls the driving unit 30 to obtain a predetermined pressure. The motor 31 is rotated at the rotation speed R. Then, in the control unit 50, the heating roller 12 when a plurality of sheets P having different thicknesses such as a thin sheet and a thick sheet are passed through the fixing pressure contact part N based on a detection signal from the rotation speed detection unit. Is measured. Further, based on the detection signal from the photosensor 16, the linear velocity V of the sheet P at that time is measured. Besides the preliminary measurement, the rotation speed r of the heating roller 12 and the linear velocity V of the sheet P may be obtained by simulation or the like.

  FIG. 2 shows an example of a graph organized by the relationship between the thickness t of the sheet P and the rotation speed r of the heating roller 12 with respect to the measurement result. The relationship between the rotation speed r of the heating roller 12 and the linear velocity V of the sheet P An example of the organized graph is shown in FIG. Relation information (for example, an information table or a calculation formula) indicating the relations shown in FIGS. 2 and 3 is stored in a storage unit such as a ROM provided in the control unit 50. And the control part 50 uses the said relationship information, with respect to the linear velocity of the sheet | seat P when rotating the motor 31 with a certain rotation speed, the heating roller 12 for conveying with the target linear velocity. The required amount of change in the rotational speed can be obtained.

  In the fixing device 100, even when the rotation speed of the fixing roller 11 is constant, the fixing roller 11 has an elastic layer. Therefore, the fixing roller 11 has its own thermal expansion, a difference in thickness of a sheet to be passed, and the like. The peripheral speed of fluctuates. Therefore, the linear speed of the fixing belt 14 rotated by the fixing roller 11, that is, the linear speed (conveying speed) of the sheet P also varies. In the fixing operation, the control unit 50 measures the number of rotations of the heating roller 12 and obtains a necessary change amount of the number of rotations of the heating roller 12 for setting the linear velocity of the sheet P as a target value. The control unit 50 adjusts the rotation number of the motor 31 by controlling the drive unit 30 so that the rotation number of the heating roller 12 changes by the necessary change amount. Thereby, the linear velocity of the sheet | seat P can be made into a target value.

  In the preliminary measurement, the rotational speed r of the heating roller 12 and the linear velocity V of the sheet P are measured for a plurality of sheets P having different thicknesses, and the relationship between them is derived. However, the present invention is not limited to this. Absent. For example, instead of the paper thickness, the rotational speed r of the heating roller 12 and the linear velocity V of the sheet P are similarly measured for a plurality of sheets P having different paper qualities such as coated paper and non-coated paper, and the relationship between them is measured. It may be derived. Alternatively, in the preliminary measurement, the number of rotations of the heating roller 12 in a non-sheet passing state is measured, and the necessary change of the heating roller for conveying the sheet having the next thickness to be passed at the target linear speed based on the measurement result It is also possible to determine the quantity.

  Further, feedback control based on the rotation speed of the heating roller 12 may be performed in the control unit 50 without performing the preliminary measurement. Specifically, the control unit 50 feeds back the rotation speed of the heating roller 12 during the fixing operation so that the rotation speed of the heating roller 12 becomes, for example, a predetermined value at which the linear velocity of the fixing belt 14 becomes a target value. Thus, the rotation driving of the fixing roller 11 by the driving unit 30 may be controlled. The control unit 50 controls the rotational driving of the fixing roller 11 so as to suppress fluctuations in the linear velocity of the fixing belt 14.

  In the fixing device 100 of the present embodiment described above, the endless fixing belt 14, the fixing belt 14 is stretched, the fixing roller 11, and the heating roller 12 and the tension roller 13 that are rotated as the fixing belt 14 rotates. And have. Further, the fixing device 100 is configured so that the rotatable pressure roller 15 disposed so as to press the outer peripheral surface of the fixing roller 11 against the outer peripheral surface of the fixing roller 11 via the fixing belt 14 and the fixing belt 14 are rotationally moved. And a drive unit 30 that rotationally drives the fixing roller 11. When the sheet P on which the toner image is formed passes between the fixing belt 14 and the pressure roller 15 (fixing pressure contact portion N), the toner image is fixed on the sheet P. In addition, the fixing device 100 includes a rotation speed detection unit 40 that detects the rotation speed of the heating roller 12 and the rotation speed of the heating roller 12 detected by the rotation speed detection unit 40. And a control unit 50 that controls rotational driving.

  In addition, the fixing device 100 further includes a control unit 50 in which relationship information indicating the relationship between the rotation speed of the heating roller 12 and the linear velocity of the fixing belt 14 is stored. Then, the control unit 50 controls the rotation driving of the fixing roller 11 by the driving unit 30 based on the rotation number of the heating roller 12 detected by the rotation number detection unit 40 and the relationship information stored in the control unit 50. It is configured as follows.

  As described above, according to the present embodiment, the fixing roller 11 is rotationally driven by the driving unit 30 so that the fixing belt 14 is rotated. The rotation speed detector 40 detects the rotation speed of the heating roller 12. The controller 50 controls the rotation of the fixing roller 11 by the drive unit 30 based on the rotation number of the heating roller 12 detected by the rotation number detector 40. With such a configuration, the rotation speed of the heating roller 12 on which the fixing belt 14 is stretched has a correlation with the linear speed (surface movement speed) of the fixing belt 14, and therefore the line of the fixing belt 14 is based on the rotation speed. You can grasp the speed. Therefore, by controlling the driving unit 30 based on the number of rotations of the heating roller 12, the linear velocity of the fixing belt 14 can be grasped without processing the fixing belt 14 or adding a member such as a roller. It is possible to control so as to suppress fluctuations in the linear velocity. As a result, it is possible to suppress both a change in the conveyance speed of the sheet P and a decrease in durability of the fixing belt 14 with an inexpensive configuration.

  In addition, relationship information indicating the relationship between the number of rotations of the heating roller 12 and the linear velocity of the fixing belt 14 is stored in the control unit 50. Then, the control unit 50 controls the rotation driving of the fixing roller 11 by the driving unit 30 based on the rotation number of the heating roller 12 detected by the rotation number detection unit 40 and the relationship information stored in the control unit 50. It is configured as follows. Therefore, the control unit 50 controls the drive unit 30 using the relationship information indicating the relationship between the rotation speed of the heating roller 12 and the linear velocity of the fixing belt 14 created based on preliminary measurement or the like, so that the accuracy is higher. Control becomes possible, and thereby fluctuations in the conveyance speed of the sheet P can be further suppressed.

(Embodiment of Image Forming Apparatus)
Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.

  FIG. 4 shows the configuration of a tandem type color copying machine which is an image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 4, the color copying machine 200 includes an image forming unit 200A located at the center of the apparatus main body, a paper feeding unit 200B located below the image forming unit 200A, and an image forming unit 200A. And a high-speed machine having an image reading unit (not shown). In the color copying machine 200, the fixing unit 100 configured by the above-described fixing device 100 is incorporated between the image forming unit 200A and the paper feeding unit 200B and downstream of the image forming unit 200A in the sheet conveying direction. .

  The image forming unit 200A is provided with a transfer belt 210 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the transfer belt 210. Is provided. That is, photosensitive members 205Y, 205M, 205C, and 205K as image carriers capable of carrying an image of complementary color toners (yellow Y, magenta M, cyan C, and black K) are formed on the transfer surface of the transfer belt 210. Are juxtaposed along.

  Each of the photoconductors 205Y, 205M, 205C, and 205K includes a drum that can rotate in the same direction (counterclockwise direction in the figure). For example, an optical writing device 201, a charging device 202Y, a developing device 203Y, a primary transfer device 204Y, and a cleaning device (not shown) that perform image forming processing in the rotation process are disposed around the photosensitive member 205Y. For each of the photoconductors 205M, 205C, and 205K, each device is arranged around the photoconductor 205Y.

  Each developing device 203Y, 203M, 203C, 203K contains a respective color toner. The transfer belt 210 is configured to be able to move in the same direction at a position facing the photoconductors 205Y, 205M, 205C, and 205K by being wound around a driving roller and a driven roller. Further, a transfer roller 212 is provided at a position facing a roller 211 which is one of the driven rollers. Further, the conveyance path of the sheet P from the transfer roller 212 to the fixing device 100 is a horizontal path.

  The sheet feeding unit 200B separates the sheet P in the sheet feeding tray 220 one by one from the top in order from the top to the position of the transfer roller 212. A conveyance mechanism 221 for conveying is provided.

  In forming an image in the color copying machine 200, the surface of the photoreceptor 205Y is uniformly charged by the charging device 202Y, and an electrostatic latent image is formed on the photoreceptor 205Y based on image information from the image reading unit. The electrostatic latent image is visualized as a toner image by a developing device 203Y containing yellow toner, and the toner image is primarily transferred onto the transfer belt 210 by a primary transfer device 204Y to which a predetermined bias is applied. Is done. The other photoconductors 205M, 205C, and 205K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the transfer belt 210 by the electrostatic force and superimposed.

  Next, the toner image T primarily transferred from the photoconductors 205Y, 205M, 205C, and 205K onto the transfer belt 210 is transferred to the sheet P conveyed by the rollers 211 and 212. The sheet P on which the toner image T has been transferred is further conveyed to the fixing device 100 and is fixed at a fixing nip N (fixing pressure contact portion N) between the fixing belt 14 and the pressure roller 15. The sheet P that has passed through the fixing nip portion N is not wound around the fixing belt 14 and the pressure roller 15 by the first separation claw 18 and the second separation claw 19 disposed on the downstream side. It is discharged to the downstream side. Next, the sheet P discharged from the fixing nip N is sent out to the stacker 213 along the discharge path.

  The color copying machine 200 of the present embodiment includes an image forming unit 200A that forms a toner image on a sheet P, and a fixing unit 100 that fixes the toner image formed on the sheet P by the image forming unit 200A to the sheet P. At least. The fixing unit 100 is the fixing device 100 according to the above-described embodiment. With such a configuration, according to the color copying machine 200, the rotation speed of the heating roller 12 on which the fixing belt 14 is stretched has a correlation with the linear speed of the fixing belt 14 in the fixing unit 100. The linear velocity of the fixing belt 14 can be grasped based on the above. Therefore, by controlling the driving unit 30 based on the number of rotations of the heating roller 12, the linear velocity of the fixing belt 14 can be grasped without processing the fixing belt 14 or adding a member such as a roller. It is possible to control so as to suppress fluctuations in the linear velocity. As a result, it is possible to suppress both a change in the conveyance speed of the sheet P and a decrease in durability of the fixing belt 14 with an inexpensive configuration.

  While the present invention has been described with reference to a preferred mobile phone, the present invention is not limited to the configuration of the above embodiment.

  For example, in the fixing device 100 of the above-described embodiment, the rotation number detection unit 40 detects the rotation number of the heating roller 12, but the present invention is not limited to this. For example, the rotation number detection unit 40 may be configured to detect the rotation number of the tension roller 13 instead of the heating roller 12, or may be configured to detect both the rotation number of the heating roller 12 and the tension roller 13. That is, if the rotational speed detection unit 40 is configured to detect the rotational speed of a roller (driven roller) that is rotated with the rotational movement of the fixing belt 14, the rotational speed is detected unless the object of the present invention is contrary. The roller which becomes the object to perform is arbitrary.

  In the color copying machine 200 of the above-described embodiment, a full-color tandem type image forming apparatus in which a plurality of photoconductors are arranged in a line has been described. However, the present invention is not limited to this. For example, it may be a monochrome image forming apparatus having only one photoconductor or a revolver type image forming apparatus, as long as it has at least an image forming part and a fixing part, as long as the object of the present invention is not violated. The configuration of the image forming apparatus is arbitrary.

  The above-described embodiments are merely representative examples of the present invention, and the present invention is not limited to the embodiments. That is, those skilled in the art can implement various modifications in accordance with conventionally known knowledge without departing from the scope of the present invention. Of course, such modifications are included in the scope of the present invention as long as the configurations of the fixing device and the image forming apparatus of the present invention are provided.

11 Fixing roller 12 Heating roller (an example of a driven roller)
13 Tension roller (an example of a driven roller)
14 Fixing belt 15 Pressure roller (an example of a pressure member)
16 Photosensor 30 Drive part (an example of drive means)
40 Rotational speed detection unit (an example of rotational speed detection means)
41 Filler 42 Heating roller rotation detection sensor 50 Control unit (an example of control means and storage means)
100 fixing device 200 color copying machine (an example of an image forming apparatus)
200A Image forming unit 200B Paper feeding unit 202Y, 202M, 202C, 202K Charging device 203Y, 203M, 203C, 203K Developing device 204Y, 204M, 204C, 204K Primary transfer device 205Y, 205M, 205C, 205K Photoconductor 210 Transfer belt 212 Transfer roller 220 Paper feed tray N Fixing pressure contact portion P sheet (an example of a recording medium)

JP 2012-13821 A JP 2011-28038 A Japanese Patent No. 3382403 JP 2010-72480 A

Claims (3)

An endless fixing belt,
A roller group including one or a plurality of driven rollers on which the fixing belt is stretched and rotated in accordance with the rotational movement of the fixing roller and the fixing belt;
A rotatable pressure member arranged to press the outer peripheral surface of the fixing roller against the outer peripheral surface of the fixing roller via the fixing belt;
Drive means for rotationally driving at least one of the fixing roller and the pressure member so that the fixing belt is rotated;
A rotational speed detection means for detecting the rotational speed of at least one driven roller of the one or more driven rollers;
Control means for controlling the rotational drive by the drive means based on the rotational speed of the driven roller detected by the rotational speed detection means;
A fixing device. Storage means for storing relationship information indicating the relationship between the rotational speed of the driven roller and the linear velocity of the fixing belt;
The control means is configured to control the rotational drive by the drive means based on the rotational speed of the driven roller detected by the rotational speed detection means and the relation information stored in the storage means. The fixing device according to claim 1, wherein the fixing device is provided. An image forming apparatus comprising at least an image forming unit that forms a toner image on a recording medium, and a fixing unit that fixes the toner image formed on the recording medium by the image forming unit to the recording medium.
The image forming apparatus, wherein the fixing unit is the fixing device according to claim 1.

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